This invention relates to the field of glass melting and in particular relates to the melting of pulverized glass batch concurrent with the combustion of a fuel in a high temperature vortex melting system.
In presently available gas or oil fired glass melting operations, the glass product is formed by melting mineral matter (glass batch) in an open-hearth type furnace. Many design changes have been incorporated into these furnaces since the original patents obtained by the Siemens family in the late 1800's. However, the fundamental heat transfer mechanisms for melting the glass batch are still quite similar to those in the original furnaces. Because open-hearth furnaces primarily rely on radiation from the flame and crown for heat transfer to the batch being melted, the surface area of the melter is necessarily large. This large surface area, even with substantial insulation, leads to wall heat transfer losses which are in the order of 20 per cent of the thermal input into the melter. Thses high wall heat transfer losses coupled with the heat losses associated with the stack gas and glass product sensible heat are the major factors contributing to the low operating efficiency of current furnace designs. Typical heat rates for current furnace designs range from 5.0 million Btu to 7.0 million Btu per ton of glass produced. The heat rate for the vortex melting systems of the present invention using conventional heat recovery technology is projected to be in the range of 2.9 million to 4.0 million Btu/ton without electric boosting. Projections are that heat rates as low as 2.5 million Btu/ton are possible if advanced heat recovery technology is utilized.
Numerous attempts have been made to improve furnace efficiency over the past 50 years. Descriptions of innovative glass melting concepts for which development has been attemped have been compiled by A. G. Pincus in Melting In the Glass Industry--6 volumes, Books for Industry, New York 1976. Of particular note is the furnace invented by Alexander Ferguson in 1923 which is reported to have melted 60 mesh glass batch in suspension in a refactory lined cyclone type furnace.
In addition, a number of plasma arc furnaces have also been developed which incorporate suspension melting. Several of these furnace designs are described in the "Journal of Minerals Science Engineering," Volume 9, No. 3, July, 1977. Plasma arc furnaces rely heaviy on the use of electric power for the melting process, and although different in principle from the gas or oil-fired vortex glass melting process, do demonstrate the ability to melt glass and ceramic type products in suspension.